In a resist peeling process in the manufacture of a semiconductor, a solution such as sulfuric acid is often heated and used at a high temperature as a cleaning liquid. Particularly, when a resist of a wafer is peeled by a single substrate processing washer using a electrolyzed sulfuric acid solution of which an active ingredient is persulphuric acid (peroxodisulfuric acid and peroxomonosulfuric acid) obtained by electrolysis of a sulfuric acid solution, the electrolyzed sulfuric acid solution should be rapidly (for about 5 to 10 seconds) heated from about 100° C. to a temperature of about 180° C. to 200° C. that is the service temperature in the washer. A rapid heater, which uses a near infrared heater, is proposed as a device used for this heating (see Patent Literature 1).
Generally, examples of the principle of heat transfer include (1) conduction, (2) convection, and (3) radiation.
In the rapid heater, heat needs to be transferred in a short time. Residence time in the device should be shortened to transfer heat to fluid, which has a constant flow rate, in a short time. Then, however, since a heat transfer area cannot be increased, it is not possible to transfer sufficient heat by a heat transfer method, such as (1) conduction or (2) convection. Accordingly, the rapid heater uses a method of making light be emitted from the near infrared heater and making the light be directly absorbed in molecules of the fluid, here, molecules of sulfuric acid or water. Further, the thickness of a liquid flow channel is reduced in order to shorten the residence time of liquid.
In a general heating device, the outer portion of the heating device is covered with a heat insulator so that heat is accumulated in the heating device and high temperature is maintained for high thermal efficiency. The outline of the heating device will be described with reference to FIG. 13.
A near infrared heater 101 is disposed outside a heat intended liquid flow channel 100, and a heat insulator 102 is disposed on the side opposite to the near infrared heater 101. Heat rays output from the near infrared heater 101 are emitted to the liquid-to-be-heated flow channel 100, so that a electrolyzed sulfuric acid solution flowing through the heat intended liquid flow channel 100 is rapidly heated by radiant heat. A high-temperature electrolyzed sulfuric acid solution flows out of the heat intended liquid flow channel 100.